Clathrate of azithromycin hydrate with 1,2-propyleneglycol, method for the manufacture thereof and pharmaceutical composition comprising same

ABSTRACT

A clathrate of azithromycin hydrate with 1,2-propyleneglycol is much less hygroscopic than azithromycin hydrate or crystals known in the art, therefore, it can be useful for the preparation of a medicine for treating various microbial infections.

FIELD OF THE INVENTION

This invention relates to a novel clathrate of azithromycin hydrate with1,2-propyleneglycol, a process for its manufacture, and a pharmaceuticalcomposition containing the clathrate.

BACKGROUND OF THE INVENTION

Azithromycin, 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A(N-methyl-11-aza-10-deoxo-10-dehydroerythromycin A: IUPAC) of formula(II) disclosed in U.S. Pat. Nos. 4,517,358 and 4,474,768, is anazalide-type semi-synthetic macrolide antibiotic, useful for treatingbronchial infection, sexual contact infection and dermatologicalinfection (See Kirste and Sides; Antimicrob. Agents Chemother., 33,1419(1989)).

Azithromycin is known to exist in three forms, the anhydride,monohydrate and dihydrate forms. These forms have been identified bypowder X-ray diffraction and differential scanning calorimetric studies.

Azithromycin anhydride, which is disclosed in U.S. Pat. No. 4,517,359,is non-crystalline product and thus, its highly hygroscopic property isnot suitable for pharmaceutical formulation.

Further, azithromycin monohydrate (mp. 136° C.), as described in U.S.Pat. No. 4,474,768 and WO Publication No. 89/00576, is crystalline butit has also hygroscopic property, making it difficult to maintain itswater content at a constant level.

WO Publication No. 89/00576 discloses a process for preparingazithromycin dihydrate (mp. 126° C.) from azithromycin monohydrate byrecrystallizing from a mixture of tetrahydrofuran, water and a C₅˜C₇aliphatic hydrocarbon. Although the dihydrate is less hydroscopic thanthe monohydrate, the water content thereof must be carefully maintainedduring a vaccum drying step at a relatively low temperature. Such awater content controlling procedure is, however, not sufficient forremoving the toxic aliphatic hydrocarbon solvent rigorously used in therecrystallization procedure. On the other hand, vacuum drying in highertemperature may result in formation of azithromycin dihydrate havingundesirable water content.

Accordingly, many attempts have been made to develop a novel crystal orsolvate form of azithromycin. For example, EP Publication No. 0,984,020discloses a clathrate of azithromycin monohydrate with isopropanol offormula (III).

WO Publication No. 00/32203 discloses an ethanol solvate of azithromycinhydrate of formula (IV).

However, there has existed a need to develop an improved crystal form ofazithromycin crystal suitable for pharmaceutical applications.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a novelform of azithromycin, which can be useful for the preparation of amedicine for treating various microbial infections.

In accordance with the present invention, there is provided a novelclathrate of azithromycin hydrate with 1,2-propyleneglycol of formula(I):

wherein m ranges from 1 to 2 and n, from 0.20 to 0.40.

The present invention further provides a process for preparing theclathrate of formula (I), comprising the steps of: (1) dissolvingazithromycin in acetone then adding 1,2-propyleneglycol and waterthereto to obtain a crystalline product; and (2) filtering the crystalsformed, washing the crystals with water and drying to produce theazithromycin clathrate crystals.

The present invention also provides a pharmaceutical composition fortreating microbial infection, comprising the clathrate of formula (I)and a pharmaceutically acceptable carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the invention, whentaken in conjunction with the accompanying drawings, which respectivelyshow:

FIG. 1: a powder X-ray diffraction spectrum of the compound of thepresent invention;

FIG. 2: a powder X-ray diffraction spectrum of azithromycin monohydrate;

FIG. 3: a powder X-ray diffraction spectrum of azithromycin dihydrate;

FIG. 4: a differential scanning calorimetric scan of the compound of thepresent invention;

FIG. 5: a differential scanning calorimetric scan of azithromycinmonohydrate;

FIG. 6: a differential scanning calorimetric scan of azithromycindihydrate;

FIG. 7: comparative hygroscopic properties of the compound of thepresent invention, azithromycin anhydride, monohydrate, and dihydrate.

DETAILED DESCRIPTION OF THE INVENTION

The compound of formula (I) may be prepared by (1) dissolvingazithromycin in a suitable amount of acetone, preferably 2 to 10 ml ofacetone per g of azithromycin, adding 1,2-propyleneglycol thereto in anamount of 0.25 to 2.5 nm based on 1 ml of acetone while maintaining at atemperature ranging from room temperature (R.T.) to the boiling point ofacetone, adding water in an amount of 1 to 3 ml per ml of acetone,stirring the mixture for 30 minutes to 4 hours at a, temperature rangingfrom 0° C. to room temperature, filtering precipitated crystals, washingthe crystals with water and drying for 12 to 24 hours at a temperatureranging from 40° C. to 45° C.

The 1,2-propyleneglycol moiety of the inventive clathrate is essentiallynon-toxic (LD₅₀: 25 ml/kg, at oral administration in rat), and it canexist in the form of a racemate, an S-isomer, or an R-isomer.

The azithromycin being used in the preparation of the inventiveclathrate may be anhydride, monohydrate, dihydrate, isopropanolclathrate, or ethanol solvate of azithromycin known in the art or amixture thereof, and it can be prepared by any of the methods disclosedin U.S. Pat. Nos. 4,517,359 and 4,474,768 and Korean Patent ApplicationNo. 2001-14659.

The novel clathrate compound of the present invention meltsapproximately at 130° C., shows in a DSC scan an endothermic peak at150.8° C. and heat capacity of 104.42 J/g, as shown in FIG. 4. Thesethermal properties are completely different from those of themonohydrate form (endothermic peak 145.44° C.; heat capacity: 137.37J/g) or the dihydrate form (endothermic peak 142.72° C.; heat capacity:160.15 J/g), shown in FIG. 5 and FIG. 6, respectively.

The crystal structure of the clathrate compound of the present inventiondiffers from those of the monohydrate and dihydrate form, as the powderX-ray diffraction patterns shown in FIG. 4, FIG. 2 and FIG. 3,respectively.

The water content of the inventive clathrate determined by aKarl-Fischer water analyzer ranges from 2.3 to 4.6%, preferably, from3.0 to 4.0%, more preferably, from 3.1 to 3.7%, while its1,2-propyleneglycol content determined with a gas chromatography or¹H-NMR spectroscopy ranges from 2.1 to 4.1%, preferably, from 2.4 to3.8%.

The inventive clathrate of formula (I) preferably has an m value of1.5±0.2 and an n value of 0.30±0.06.

The clathrate compound of the present invention is much less hygroscopicthan azithromycin anhydride or azithromycin monohydrate, and its watercontent remains more or less constant when stored under a humidcondition, unlike azithromycin dihydrate.

The clathrate compound of present invention can be used in formulatingvarious pharmaceutical compositions for treating various microbialinfection. Such a composition contains the inventive clathrate togetherwith pharmaceutically acceptable excipients and carriers, which may beadministrated orally, injectably, rectally, transdermally, bucally ornasally. Suitable forms for oral administration include tablets,compressed or coated pills, dragees, sachets of powder forreconstitution, hard or soft gelatin capsules, syrups and emulsions etal. Suitable forms for parenteral administration include aqueous ornon-aqueous solution, emulsion, while for rectal administration suitableforms include suppositories with hydrophilic or hydrophobic vehicles.For topical application the invention provides ointments or aerosolformulations known in the art; for transdermal delivery, there areprovided suitable delivery systems as known in the art. For nasaldelivery there are provided suitable aerosol delivery systems known inthe art.

This invention will be better understood from the Examples that follow.However, the examples illustrate, but do not limit, the invention. Thoseskilled in the art will readily appreciate that the specific methods andresults discussed are merely illustrative of the invention as describedmore fully in the claims that follow thereafter.

EXAMPLE 1

100 g of azithromycin anhydride was dissolved in 300 ml of acetone and100 ml of 1,2-propylene glycol was added thereto. The solution wasstirred for 10 minutes at R.T. and 500 mg of water was added dropwisethereto to induce the precipitation of azithromycin crystals. Thesolution was stirred for 2 hours at R.T. and the precipitate wasfiltered, washed rigorously with water, and then dried at 40° C. for 20hours to give 96 g of a clathrate of azithromycin hydrate with1,2-propyleneglycol.

m. p: 129 to 131° C.,

The water content determined by a Karl Fischer water analyzer: 3.5 wt %,The 1,2-propyleneglycol content determined with a gas chromatography:3.3 wt %.

EXAMPLE 2

20 g of azithromycin monohydrate was dissolved in 100 ml of acetone and15 ml of 1,2-propylene glycol was added thereto. The solution wasstirred for 10 minutes at R.T. and 200 ml of water was added dropwisethereto to induce the precipitation of azithromycin crystals. Thesolution was stirred for 2 hours at 0 to 5° C. and the precipitate wasfiltered, washed rigorously with water, and then dried at 40° C. for 20hours to give 18.2 g of a clathrate of azithromycin hydrate with1,2-propyleneglycol.

m. p: 130 to 132° C.,

The water content: 3.4 wt %,

The amount of 1,2-propyleneglycol: 3.2 wt %.

EXAMPLE 3

20 g of azithromycin monohydrate was dissolved in 120 mb of acetone and15 mg of 1,2-propylene glycol was added thereto. The solution wasstirred for 10 minutes at R.T. and 180 ml of water was added dropwisethereto to induce the precipitation of azithromycin crystals. Thesolution was stirred for 3 hours at 0 to 5° C. and the precipitate wasfiltered, washed rigorously with water, and then dried at 40° C. for 20hours to give 17.6 g of a clathrate of azithromycin hydrate with1,2-propyleneglycol.

m. p: 130 to 132° C.,

The water content: 3.4 wt %, The 1,2-propyleneglycol content: 3.5 wt %.

TEST EXAMPLE 1

The compound obtained in Example 1, azithromycin monohydrate anddihydrate obtained by the methods in accordance with U.S. Pat. No.5,869,629 were subjected to differential scanning calorimetricmeasurements (heat speed 10° C./minutes.). The inventive compound ofExample 1 showed an endothermic peak at 150.8° C. and heat capacity of104.42 J/g, as shown in FIG. 4. The azithraycin monohydrate, on theeother hand, showed an endothermic peak at 145.44° C. and heat capacityof 137.37 μg (FIG. 5), while azithromycin dihydrate, an endothermic peakat 142.72° C. and heat capacity of 160.15 J/g (FIG. 6).

Further, the X-ray diffraction spectra of above three compounds areillustrated in FIG. 1, FIG. 2 and FIG. 3, respectively. The X-rayresults summarized in Table 1 show that the compound of presentinvention has a crystal structure which is completely different fromthose of the known compounds.

Also, the hygroscopic properties of each of the compound obtained inExample 1 (1), azithromycin dihydrate (2), monohydrate (3), andanhydride (4) were determined by exposing each sample to a relativehumidity of each 25%, 50%, 75% or 100% for 7 days and measuring thewater content thereof by the Karl Fischer method. The result is shown inTable 2 and FIG. 7.

TABLE 1 Radiation: Cu K-α1 Operation: 40 kV/126 mA Divergence slit: 1°Scan Mode: continuous Scattering slit: 1° Scan speed: 5°/min Receivingslit: 0.15 mm Scan step: 0.02° 2 theta(°2Θ) d-value(A) I/Io(≧2) 6.20014.2437 3 7.300 12.0996 5 7.820 11.2962 32 8.220 10.7474 2 9.740 9.0733100 10.220 8.6482 2 11.140 7.9360 29 11.900 7.4308 7 12.220 7.2369 612.500 7.0754 22 13.880 6.3749 12 14.640 6.0456 16 15.220 5.8165 1215.400 5.7490 12 15.700 5.6398 6 15.940 5.5554 6 16.620 5.3296 6 16.9605.2235 10 17.220 5.1452 9 17.460 5.0750 11 18.060 4.9078 2 18.300 4.84393 18.500 4.7920 5 19.040 4.6573 12 19.660 4.5118 9 19.980 4.4403 1220.400 4.3498 10 20.860 4.2549 8 21.740 4.0846 4 22.320 3.9798 3 22.6403.9242 5 23.220 3.8275 2 23.540 3.7762 3 23.960 3.7109 3 24.520 3.6274 424.720 3.5985 3 25.260 3.5228 2 25.500 3.4902 3 26.200 3.3985 4 28.4403.1357 2 31.080 2.8751 2 33.600 2.6650 2

TABLE 2 (1) (2) (3) (4) Onset 3.50 4.58(4.1) 2.30(3.2) 0.22 Relative4.06 6.11(5.2) 6.29(7.2) 7.00 humidity 100% Relative 3.55 5.10(4.6)5.41(6.6) 4.33 humidity  75% Relative 3.50 4.25(4.6) 5.13(5.6) 2.85humidity  50% Relative 3.01 4.20(2.5) 3.35(2.3) 1.11 humidity  25% (33%) Calculated 3.38¹⁾ 4.60 2.35 0.00 water content (%) Found-−0.37~+0.68 −0.4~+1.51 +1~+3.94 +1.11~+7.00 Calculated (−2.1~+0.6)(−0.05~+4.84) (Difference, %) Range of 1.05 1.91(2.7) 3.94(4.9) 7.00Difference (%) Note: ¹⁾Calculated based on m = 1.5 and n = 0.30 informula (I). 2) The numbers in parenthesis are values obtained after 3days at the corresponding relative humidity.

Table 2 clearly shows that the novel clathrate compound of the presentinvention is much less hygroscopic than other compounds.

While the embodiments of the subject invention have been described andillustrated, it is obvious that various changes and modifications can bemade therein without departing from the spirit of the present, inventionwhich should be limited only by the scope of the appended claims.

1. A clathrate compound of azithromycin hydrate with 1,2-propyleneglycolof formula (I):

wherein m ranges from 1 to 2 and n, from 0.20 to 0.40.
 2. The compoundof claim 1, wherein water content ranges from 2.3 to 4.6% and1,2-propyleneglycol content is between 2.1 and 4.1%.
 3. A process forpreparing the azithromycin clathrate compound of formula (I) of claim 1,comprising the steps of: (1) dissolving azithromycin in acetone andadding 1,2-propyleneglycol and water thereto to obtain a crystallineproduct; and (2) filtering the crystals formed, washing the crystalswith water and drying to produce the azithromycin clathrate crystals. 4.The process of claim 3, wherein 2 to 10 ml of acetone is employed per gof azithromycin.
 5. The process of claim 3, wherein 0.25 to 2.5 ml of1,2-propyleneglycol is used per ml of acetone.
 6. The process of claim3, wherein 1 to 3 ml of water is used per me of acetone.